Influence of food web structure on the growth and bioenergetics of lake trout (Salvelinus namaycush)

Abstract

In this study, we compared energy budgets of lake trout (Salvelinus namaycush) populations in contrasting food webs. Nonpiscivorous lake trout (NPLT) reached a much smaller size and grew at a much slower rate than piscivorous lake trout (PLT) populations. Food consumption rates were, on average, 2–3 times higher in NPLT when they were expressed on a wet weight basis. However, only a slight (less than 10%) difference in their energy intake was detected once consumption rates were corrected for differences in prey caloric content. Growth efficiency was approximately two times lower in NPLT compared with PLT, while their metabolic costs were higher and their assimilation efficiency was lower. It is most likely that the increased metabolic costs were associated with higher foraging costs, since more feeding attempts must be made to acquire a given quantity of food when fish are feeding on smaller prey. Furthermore, the portion of indigestible matter is likely to be higher in the diet of NPLT than in PLT (i.e., chitin vs. bone). These results are consistent with theoretical models of fish growth that show that lake trout must have access to larger prey, even if they are rare, to reach larger body sizes.

Behavioral responses to annual temperature variation alter the dominant energy pathway, growth, and condition of a cold-water predator

“…First, increased reliance on Mysis and zooplankton would be less energetically efficient than foraging on larger prey fish or benthic invertebrates because predatory fish are more active when forced to feed on numerous, smaller prey (22). This increased energetic cost of feeding on small prey has been illustrated by studies that found predatory fish in lakes without pelagic prey fish had increased muscle activity and greater activity rates than those same species in lakes containing pelagic prey fish (23)(24)(25) and by studies showing that more active fish generally grow more slowly (26).…”

Interpreting the von Bertalanffy model of somatic growth in fishes: the cost of reproduction

“…If such a species lives in a community where a broad range of prey sizes is available, the transition to larger prey occurs smoothly as the individual grows (Paloheimo & Dickie 1966;Kerr 1971;Kerr & Ryder 1977;Piazza et al 2002), equation (2.3) is likely to hold throughout life, and potential length growth rate remains constant. If the prey field is truncated such that the availability of prey of suitable size does not keep pace with increases in predator size, then the slope of the potential growth curve (c 1 Ϫ c 2 ) will decline (dotted line in figure 1) owing to the increases in foraging costs associated with capturing relatively smaller prey (Piazza et al 2002). This decline in growth can be approximated using a new growth curve: 4) where t 1 , the intercept on the time axis for the new curve, decreases from zero in parallel with both the difference (h 0 Ϫ h 1 ) and the age at which the transition from h 0 to h 1 occurs.…”

Continental-scale variability in the feeding ecology of juvenile Chinook salmon along the coastal Northeast Pacific Ocean

“…With growth, maximum and minimum prey sizes generally increase, though the rate of change of these relationships may be modulated by species and habitat (Scharf et al 2000, Keeley & Grant 2001. These ontogenetic shifts to larger prey items may be important because growth efficiency is higher and metabolic costs are lower when feeding on larger prey (Pazzia et al 2002), and fish prey are generally higher in caloric value (Davis et al 1998).…”